The PAC announced it has hired 270 Strategies to build a field operation to marshal voter support for a potential 2016 Clinton campaign. The firm's partners include Jeremy Bird, Obama's 2012 national field director, and Mitch Stewart, who oversaw the campaign's operations in battleground states.

"There is no one that better understands grassroots presidential politics than the team that won the last two presidential elections," Craig Smith, a senior advisor to the super PAC, said in a statement. He said the firm will help mobilize the "hundreds of thousands of Americans" who are urging Clinton to run.

Clinton has been making public appearances and working on book since resigning her post at the State Department. She has not said whether she intends to seek the presidency for a second time, but the super PAC, led by longtime Clinton supporters Allida Black and Adam Parkhomenko, has begun to attract the support of several major financial backers of Clinton's 2008 White House bid and along with a handful of other big names in Democratic politics.

Smith, for instance, is a former Clinton White House political director. Last month, Sen. Claire McCaskill, D-Mo., endorsed the super PAC's effort, becoming the first sitting member of Congress to back the effort.

The group says it is creating a campaign infrastructure to assist Clinton while she makes up her mind.

"By building a strong volunteer organization now that connects with young people, women, and voters in key minority communities, the Ready for Hillary team is ensuring that if and when Hillary makes any decision about her political future, she'll have the grassroots army she needs to pave her way to victory and the White House," Bird said in a statement.

Republicans also are gearing up for a Clinton campaign. America Rising, a conservative super PAC run by Mitt Romney's former campaign manager Matt Rhoades, last month launched StopHillary2016.org â?? a site focused on raising money to oppose her candidacy.